Digital computer



March 21, 1961 J. M. FARRELL ErAL DIGITAL COMPUTER 2 Sheets-Sheet 1 Filed July '7,' 1958 d M l.

ATTO/P/VEY March 21, 1961 J. M. FARRELL ET AL DIGITAL COMPUTER Filed July 7, 1958 2 Sheets-Sheet 2 I INVENTOR ATTRNEV 2,976,459 Patented Mar. 21, 1961 2,976,459 DIGITAL COMPUTER John M. Farrell and Edward F. Weller, Jr., Detroit, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 7, 1958, Ser. No. 747,067 13 Claims. (Cl. S15-34.6)

The present invention relates to digital computers and, more particularly, to a reversible digital computer capable of counting either negatively or positively.

In one form of digital computer a gaseous-discharge tube is provided which employs acenter anode and a plurality of pins which are symmetrically arranged therearound. One group of these pins forms cathodes while the remaining pins `form two groups of guides for transferring the discharge from one cathode to another. Normally, the discharge is maintained on one of the odes. However, upon the occurrence of an event to be counted, a series of pulses are applied to the guides whichl cathode to a succeeding cathode. quence in which the guides are energized, the direction of transfer of the discharge may be controlled so that the tube is able to distinguish between positive and negative events. If it is necessary to record more events than can be handled by one tube, the tubes may be cascaded so that when the dischargehas been completely cycled around one tube, a count is transferred to the succeeding tube. Although this permits counting in a positive direction, it has been extremely diiicult, if not impossible, for the second and succeeding tubes to accurately distinguish between the occurrence of a positive Vcount and a negative count in the rst tube. Accordingly, heretofore, it has been impossible to cascade such tubes so as to form a reversible digital computer.

Therefore, it is now proposed to provide means for cascading a series of multicathode gaseous-discharge tubes so that a count may be transferred from one tube to a succeeding tube in either a positive or negative direction. More particularly,` this is to be accomplished by interconnecting the output of one counting tube with the input to a succeeding counting tube by transfer means having a gaseous-discharge tube and a pair of gating circuits. The transfer tube includes a pair of cathodes interconnected with the input to the lirst counting tube so that the discharge therein will be maintained on the first cathode of the transfer tube if the discharge in the counting tube is moving in a positive direction and on the second cathode of the transfer tube if the discharge in the counting tube is moving in a negative direction. The two gating circuits are interconnected with the two cathodes and, as a result, will be actuated in response to the direction vof the count in the rst tube. These gates also interconnect the output of the first counting tube with the input of a succeeding counting tube. 4As a result, one or the other of the gating circuits will transfer a negative or positive coun-t to the succeeding tube whenever the discharge in the preceding counting tube con1- pletes a cycle in a negative or positive direction respectively. It may thus be s'een that any number of tubes may be cascaded so as to count any combination of positive and/ or negative events.

In the two sheets of drawings:

Figure l is a schematic wiring diagram of a digital computer embodying the present invention.

cathwill cause the discharge to be transferred from one By Varying the se-' Figure 2 is a series of wave forms present in various portions of the circuit of forward or positive events.

Figure 3 is a series of wave forms present in various portions of the circuit of Figure l when counting a series of reverse or negative events.

Referring to the drawings in more detail, the present K invention is adapted to be embodied in a reversible digital counter 'or computer 11 for counting or recording a series of positive and/or negative events such as increments of forward, and reverse movement of a member. y

11 comprises a trigger section 12 The present counter for producing pulses corresponding to the events to be recorded, a series of cascaded decade 'counting tubes 13 and 14 for recording the pulses, and also a transfer cir.- cuit 15 for transferring a negative or positive countfrom one decade tube 13 to the succeeding decade tube 14.

The present trigger section 12 includes tosensitive elements 16 and 17 arranged to scan the movement of a member (not shown). rl`he photosensitive elements 16 and 17, which are interconnected with a voltage source 18 and load resistors 19 and 21, are arranged to produce voltage pulses across the resistors 19 and 21 for each equal increment of movement of the member. These pulses form pulse trains E1 and E2 (Figures 2 and 3). The photosensitive elements 16 and 17 are displaced so that the corresponding pulses in the two trains El and E2 will not occur simultaneously, but instead, will occur in a sequence dependent upon Ythe direction ofthe movement of the member past the photo# sensitive elements 16 and 17. For example, when the member is moving in a forward direction and/or it is desirable tocount in a positive direction, the pulses in train E2 will precede the pulses in train El (Figure 2,). However, when the member is moving in a reverse direction and/or it is desirable to count in a negative direction, the pulses intrain E1 will precede the pulses in train E2 '(Figure`3).`

The load resistors 19 and 21 are interconnected with the inputs 22-23 and 24 25 to a pair of substantially identical D.C. amplifiers 26 and 27 .adapted to be triggered `by the pulses in trains E1 and E2. The outputs 2.9 and 31 of these amplifiers 26 and 27 will comprise a second pair of pulse trains a separate square wave pulse for each of the pulses across the load resistors 19 and 21. The sequence of the pulses in trains E4 and E5 are the same as the corresponding pulses in trains E1 and E2 duration of each of the square pulses ment of the corresponding pulse in the other train. However, the irst pulse terminates prior to termina-tion of the corresponding pulse in the other train.

The decade counting tubes 13 and 14are of the socalled counting tube type. central electrode which acts as the anode 32 rounded by a plurality of cathodes. rst tube are numbers 1, 2, '3, 4, 5, 6, 7, 8, 9 and-10 and -those in the second tube are numbers 10, 20, 30, 40, 50, 60, 70, ,80, and 100. Each cathode is interconnected with ground by a Vseparate load resistor. In adand is `surrdition, interspersed between the cathodes 0 to 9 in the rst tube 13 is a rst group 33 of guide pins and asecond group 34 of guide pins. These groups `are only schematically shown in thev drawings. All of the guide pins in the rst group 33 are positioned on one side of the of Figure 1 when counting a series` a pair of phol E., and E5 consisting of* and, although thel is very short, the f f leading pulse in one train continues past the commencegaseous discharge multicathode glow transfer` Each tube 13 and 14 comprises kav The cathodes in the from the second DC. amplifier 27. Since the maintaining voltage is substantially less than the breakdown voltage, the discharge will normally remain between some particular cathode and the anode. However, if a negative pulse froml the first D.C. amplifier 26 is applied to the first group 33 of guide pins, the` discharge will transfer from a cathode to the guide pin in the first group 33 closest thereto. If a second negative pulse from the second D.C. amplifier 27 is then applied to the second group 34 of guide pins and the first pulse terminated, the discharge will move to the adjacent guide pin in the second group 34. Upon termination of the second pulse, the discharge will move to the adjacent cathode and the tube 13 will have counted one positive or forward event. If the sequence in which the negative pulses are applied to the guide pins 33 and 34 is reversed the discharge will be transferred in the opposite direction from cathode to cathode around the tube.

It will thus be seen that the events as sensed by the photosensitive elements 16 and 17 will cause a transfer of the discharge in the tube 13 for each. event andv in a direction corresponding to the sequence of the events. If it is necessary to count to a greater amount than can be handled by a single decade tube 13, a second decade tube 14 may be cascaded with the first tube 13. The second tube 14 is substantially identical to the first decade tube in that it includes a plurality of cathodes l0, 20,

30, 40, 50, 60, 70, 80, 90 and 1GO having first and second A groups 35 and 36 of guide pins interspersed therebetween. Thus, whenever the discharge completely cycles around the first tube and settles on the number 9 or O cathode, a voltage will appear across the corresponding cathode resistor 37 or 38 to produce `a control pulse for triggering the transfer of the discharge in the second decade tube from one cathode to an adjacent cathode.

in order to enable the second decade tube 14- to record a positive or negative count every time the discharge completes a cycle around the first decade tube in a positive or negative direction respectively, the transfer circuit 15 is provided. The transfer circuit 15 includes a multicathode discharge tube which functions as an addsubtract transfer tube 39. In addition, there is a forward gate 41 and a reverse gate 42 that are controlled by the transfer tube 39. The transfer tube 39 may be similar to the decade tubes. However, only a pair of adjacent cathodes 43 and 44 are connected to ground by load resistors 45 and 46. The first and second guide pins 47 and 48 between these cathodes are connected to the outputs 29 and 31 of the first and second D.C. amplifiers 26 and 27 respectively. All of the remaining cathodes and guide pins are not connected.

The forward gate 41 includes a control input 43' that is interconnected with the load resistor 45 for the positive or forward cathode 44 in the transfer tube 39. IThis input 43' will allow the gate 41 to normally be inoperative but when there is a predetermined positive potential thereon, as caused by conduction of the positive or forward cathode 44. the gate 41 will be conductive. A second input 49 thereto is interconnected with the load resistor 3S for the 0 cathode. This input 49 is adapted to receive a pulse and, if the gate 41 is operative, to transmit a corresponding pulse to the output.

The reverse gate 42 is similar to the forward gate 41 except the control input 51 is connected across the load resistor 4S for the negative or reverse cathode 43 so as to be responsive to the potential thereacross. The other input 52 is connected across the load 37 for the 9 cathode.

The output 53 of the forward gate 41 is connected to a first multivibrator 54 and the output 55 of the reverse gate 42 is connected to a second multivibrator 56. These multivibrators 54 and 56 each have a pair of outputs 58 and 59 that are connected to the inputs of a pair of multiplexes 61 and 62. Each multiplex 61 and 612 has one output 63 or 64 that is connected to the guide pins in one of'the groups 35 or 36in the second decade tube 14.

It will thus be seen that, if the pulses in the pulse trains E4 and E5 are occurring in a positive or forward sequence, these pulses will cause the first decade tube 13 to count in a positive or forward direction. Simultaneously with the first count in the first decade tube 13, the pulses E1 and E5 will also cause the discharge in the transfer tube 39 to move to the positive or forward cathode 44. As long as the pulses are occurring in a positive sequence, the discharge` will remain settled on the positive or forward cathode 44. As a result, the voltage E5 across the resistor will rise to a predetermined positive amount and cause the positive or forward gate 41 to be operative. At the same time voltage E1 across the negative or reverse cathode load resistor 45 will be zero and the negative or reverse gate 42 will be inoperative. Thus, whenever the discharge is transferring in a positive direction around the first decade tube 13 and settles on the 0 cathode, the voltage E8 across the resistor 38 will change and produce a positive signal E8 which will pass through the gate 41 and appear as E10 at the input to the multivibrator 54. The output E11 from the reverse gate 42 will remain zero. The outputs from the multivibrator will comprise E12 which is a positive pulse and E13 which includes a negative pulse and a positive pulse. These pulses will be fed into the multiplexes 61 and 62 and be inverted to form a negative pulse E15 and a positive and negative pulse E17. These pulses are applied to the first and second groups 35 and 36 of guide pins in the second decade tube 14. Since the pulse E16 occurs first the discharge will transfer in a positive direction to they adjacent guide pin in the first group 35. The negative pulse in E17 will then occur during the termination of the pulse E15 and the discharge will move in a positive direction to the adjacent guide pin in the second group 36. When this pulse terminates the discharge will move in a positive direction to the adjacent cathode. Thus, whenever the discharge completes a positive cycle around the first decade tube 13, the discharge in the second decade tube 14 will advance one cathode.

lt is, of course, apparent that if the pulses in trains E., and E5 are occurring in a negative or reverse sequence, the reverse process will occur. That is, the pulses in E5 and E5 will cause the discharge in the transfer tube 39 to settle on the negative or reverse cathode 43. Thus E.; will be zero and E7 will be positive and forward gate 41 will now be inoperative and the reverse gate 42 operative. In the event the discharge in the first decade tube 13 is traveling in a negative direction and settles on the 9 cathode, a positive signal E9 will appear at the input to the reverse gate 42 and be transmitted as E11 to the multivibrator 56. This will trigger the multivibrator to produce a positive pulse E14 and negative and positive pulses E15. The multiplexes 61 and 62 will invert these and apply the pulses E15 and E17 to the guide pins 35 and 36 to transfer the discharge in the second decade tube 14 in a negative direction.

It is to be understood that, although the invention has been described with specific reference to a particular embodiment thereof, it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

What is claimed is:

l. In a device of the class described, a first multicathode gaseous-discharge tube, having output electrodes, pulse means to cycle a discharge around said tube in either direction, control means for deriving a control pulse whenever said discharge reaches an output electrede of said tube, a second multicathode gaseous-discharge tube, transfer means connected directly with said pulse means and with said control means, said transfer means being effective to cycle said second discharge aereas@ around said second tube in response to said control pulse and said pulse means in a direction corresponding to the direction of discharge transfer in said first tube.

2. In a device of the class described, a first multicathode gaseous-discharge tube, having output electrodes, a pulse means to cycle a discharge around said tube in either direction, a second multicathode gaseous-discharge tube, means for deriving 'a control pulse whenever said discharge reaches an output electrode of said tube, a positive gate circuit and a negative gate circuit interconnected With said output electrodes and responsive to the direction of transfer of the discharge in said first tube whereby one or the other of Vsaid gate circuits will be operative in response to said direction,` said operative gate being effective to transfer the discharge in said second tube in response to said control pulse and in a direction corresponding to the direction of transfer in said first tube, and means connectedv with said pulse means and gate circuits for applying control signals to said gate circuits to control the conduction thereof.

3. In a device of the class described, a first multicathode gaseous-discharge tube having output electrons, pulse means to cycle a discharge aroundsaid tube in either direction, means for deriving a control pulse whenever said discharge reaches an output electrode of said tube, a gaseous discharge tube having at least a pair of cathodes responsive to said pulse means for transferring a discharge to one or the other of said last mentioned cathodes depending on the direction of transfer in said first tube, a second multicathode gaseous-discharge tube, gating mean-s actuated by said pair of cathodes and responsive to said control pulse for transferring the discharge in said last tube in a direction corresponding to the direction of discharge transfer in said first tube.

4. In a device of the class described, a first multicathode gaseous-discharge tube having output electrodes, pulse means to transfer said discharge from cathode to cathode around said tube in either direction, a second multicathode gaseous-discharge tube, means for transferring `a discharge from cathode -to cathode around said second tube in either direction, means for deriving a control pulse from said first tube whenever said discharge completes a cycle and reaches an output electrode lof said tube, a positive gate circuit, a negative gate circuit, said gate circuits being interconnected with the input to said second tube and alternatively actuated in response to the direction of transfer in said first tube, said operative gate circuit being responsive to said control -pulse for transferring the discharge in said second tube to an adjacent cathode and in a direction corresponding to the direction of vtransfer in the first tube, and means connected With said pulse means and gate circuits for applying control signals to said gate circuits to control the conduction thereof.

5. In a device of the class described, a first multicathode gaseous-discharge tube having a plurality of cathodes, pulse means to transfer said discharge from cathode to cathode around said tube in either direction, a second multicathode gaseous-discharge tube having a plurality of cathodes, means for transferring a discharge from cathode to cathode around said second tube in either direction, a gaseous-discharge tube having at least a pair of cathodes responsive to said pulse means for transferring a discharge to one or the other of said last mentioned cathodes depending on the direction of transfer in said first tube, a positive gate circuit, a negative gate circuit, said gate circuits `being operatively interconnected with said pair of cathodes and with said first and second tubes for transferring the discharge in said second tube in a direction corresponding to the direction of transfer in said first tube whenever the discharge therein completely cycles around the first tube.

6. A reversible electronic counter comprising a first counting tube having a plurality of vdischarge cathodes, means for sequentially transferring said discharge Afrom one cathode to an adjacent cathode on either side there-r of, Vsaid means being responsive to a pair of pulse trains for transferring-said discharge yfrom one cathode tok an adjacent cathode as a result of a pulse in each train with' the direction of transfer being determined by the sequence of the pulses in said trains, a second tube having a first and second cathode, and means responsive to the sequence of the pulses in said pulse trains for retaining said discharge on onev or the other of said cathodes depending upon the sequence of the pulses in said trains, a second counting tube having ya plurality of discharge cathodes, means responsive to the discharges in said first andvsecond tubes for transferring the'dis' charge insaid s'econdvtulbe Ito an adjacent cathode Whenpair of pulse trains for transferring said discharge from` one cathode to an adjacent cathode as a result of a pulse in each train with the direction of transfer 'being determined by the sequence of the pulses in said trains, means for deriving a control pulse whenever said discharge reaches an output electrode of said tube, asecond tube having' first and second cathodes, and means responsive to the sequence of lthe corresponding pulses in said pulse trains for retaining said discharge on one or the other `of said cathodes depending upon the sequence of the pulses in said trains, a second counting tube having a plurality of discharge cathodes, a first -gate circuit and a second gate circuit interconnected with said first and second cathodes to be `actu-ated lby Whether the discharge is on the first or second cathode, said gate circuits being effective to transfer' the discharge in said last mentioned tube from one cathode to another cathode therein in response to said control pulse and in a direction corresponding to the sequence of said pulses.

8. In a device ofthe class described, a first multicathode discharge tube having a pairy of output electrodes, pulse means to cycle a discharge around said tube in either direction, a second multicathode discharge tube having control electrodes, means for deriving a control pulse Whenever said discharge reaches one of said pair of output electrodes of said first tube, a positive gate circuit and a negative gate circuit yconnected with said output electrodes `and with the control electrodes of said second tube, and control means connected with said pulse means and said gate circuits for controlling the conduction of said gate circuits in response to the voltage wave form of said pulse means.

9. The circuit according to claim 8 wherein the control means comprises a third multicathode discharge tube.

l0. In a device of the class described, a first multicathode discharge tube having a pair of output electrodes, pulse means to cycle `a discharge around said tube in either direction, a second multicathode discharge tube having control electrodes, means for deriving a control pulse IWhenever said discharge reaches one of said pair of output electrodes of said first tube, positive and negative gate means connected with said output electrodes and with the control elect-rodes of said second tube, and control means operated by said pulse means for controlling the conduction of said gate means.

11. In a device of the class described, a first multicathode discharge tube having a pair of output electrcdes, pulse means to cycle a dischargearound said tube.` in eitherr direction, a second vmulticathode discharge Vtube having control electrodes, positive and negative gate means connecting the output electrodes of said first discharge'k tube with the control electrodes of said second discharge j tube, and means for controlling the conduction of said gate means in accordancewith the output of said pulse means.

12. In a device of the class described, a first multicathode discharge tube having a pair of output electrodes, pulse means to cycle a discharge around said tube in either direction, means for deriving a control pulse whenever said discharge reaches one of said pair of out put electrodes of said rst tube, a second multicathode discharge tube having control electrodes, and means including positive and negative gate means operated'by said pulse means for controlling a path for transferring said control pulse to the control electrodes of said second multicathode discharge tube.

13. In a device of the class described, arstmu1ticathode discharge tube having a pair of output electrodes,

transfer meansV controlled by said pulse means for transferring Said control pulse to the control electrodesof said second discharge tube.

References Cited in the tile of this patent UNITED STATES PATENTS Acton Dec. 10, 1957 Hayes May 6, 1958 Bray Sept. 9, 1958 Notice of Adverse Decision in Interference In Interference N o. 913,355 involving Patent N 0. l2,976,459, J. M. Farrell and E. F. Weller, J r., Digital computer, final judgment adverse t0 the patentees Was rendered June 22, 19647 as to claims l, 2, 4, 8, 9, 10, 11, 1'2 and 13.

[Oficial Gazette August 25, 1964.] 

